Hydrodynamics and solid—liquid contacting effectiveness in an upflow multiphase reactor

Abstract

Experimental runs were carried out in a fixed bed upflow pilot reactor to investigate the hydrodynamics of the liquid phase. Three kinds of packing were used: 3 × 3 mm glass cylinders, 3 × 4 mm alumina cylinders and 1.7 × 4 mm alumina extrudates. A tracer injection technique was used and the dynamic responses were interpreted using three different models: the axial dispersion model (PD), the stagnant zones model (PE) and the axial dispersion and stagnant zones model (PDE). Solid—liquid contacting effectiveness was evaluated by measuring the apparent intraparticle diffusivities of porous particles in the presence of the gas—liquid flow. The experimental results led to the following conclusions: (a) the axial dispersion model (PD) is not able to give a satisfactory interpretation of liquid hydrodynamics; (b) the flow map of upflow multiphase reactors is not yet well enough defined, especially for small size packings; (c) the estimate of the pressure drop by correlations in the literature is sufficiently good; (d) solid—liquid contacting effectiveness is higher, on average, than in trickle-bed reactors, but it decreases with an increase in gas flow rate.